CHEMICAL HISTORY OF THE GRATIOLA. 285 
understand the elementary composition of these substances ; 
but it is a subject of study which, it appears, must lead to 
interesting results, and it would be desirable that chemists 
placed in favourable situations to undertake such a task 
would busy themselves with it. I am persuaded they would 
be amply repaid for their trouble. 
After this digression, I again take up the description of 
the chemical characters of gratiolin. 
Nitric acid dissolves it without discoloring it. 
Chlorohydric acid dissolves it, and it assumes a yellow 
color. 
Caustic potash communicates a dirty green color to it, 
which afterwards passes into a greenish yellow, and finally 
into white. 
Caustic ammonia communicates to it a blue color, well 
marked, but without being beautiful. The reaction quickly 
takes t place, and in a short time the mass again becomes 
white. It is useful to observe that, under the influence of 
these two agents, gratiolin does not dissolve in the alkaline 
liquor. 
The extract of oak galls precipitates gratiolin from its 
watery solution, if the latter is perfectly neuter or slightly 
alkaline. If it is alkaline, the precipitation does not take 
place, for the tannate of gratiolin is soluble in liquor am- 
moniae. 
The etherous liquid, of which I have spoken above, hav- 
ing been evaporated, has left, as a residuum, a white un- 
crystallised substance, slightly bitter, insoluble in water, 
soluble in alcohol at 104°, capable of being precipitated from 
this solution by water, soluble also in ether. This sub- 
stance is acted on by fire in the same manner as gratiolin, 
from which it differs, however, inasmuch as concentrated 
sulphuric acid slowly dissolves it, acquiring a yellowish- 
brown color, slightly tinged with red. But everything in- 
duces me to believe that the color developed under these 
circumstances would be simply yellow, if the substance on 
